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PDF BU21025GUL Data sheet ( Hoja de datos )
| Número de pieza | BU21025GUL | |
| Descripción | 4-wire Resistive Touch Screen Controller | |
| Fabricantes | ROHM Semiconductor | |
| Logotipo |  |
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Datasheet
4-wire Resistive
Touch Screen Controller
BU21025GUL
●General Description
BU21025GUL is a low power 4-wire resistive touch
screen controller. BU21025GUL measures coordinates
and touch pressures with a 12bit A/D converter.
BU21025GUL has a digital filter for noise reduction.
●Features
■ 4-wire resistive touch screen controller
■ Single 1.65V to 3.60V supply.
■ Low standby current ( 0.8uA max)
■ 12bit SAR A/D converter
■ 2-wire serial interface
■ Command base interface
■ Digital filter
■ Touch pressure measurement
■ Auto power down control
■ Built-in clock oscillation circuit
●Key Specifications
■ Power supply voltage
■ Temperature range
■ Standby current
■ Operating current
■ Coordinate resolution
1.65V to 3.60V
-30℃ to 85℃
0.8uA (Max.)
120uA (Typ.)
12Bits
●Package
VCSP50L2
W (Typ.) x D (Typ.) x H (Max.)
2.00 mm x 1.50 mm x 0.55mm
●Applications
■ Equipment with a built in user interface of 4-wire
resistive touch screen
■ Portable device such as smart phone, tablet, PDA.
■ Digital still camera, digital video camera, portable
TV.
■ PC / PC peripheral equipment such as laptop PC,
touch screen monitor, printer.
●Typical Application Circuit
VDD
3
1.0μF 0.1μF
GND
Auxilary Input
10Ω
10Ω
0.1μF
0.1μF
AUX
XP
YP
Touch
Screen
1
10Ω
0.1μF
XN
10Ω
0.1μF
YN
5
GND
4
1. 4-wire resistive touch screen
2. Pull-up resistor for 2-wire serial interface
3. Bypass capacitors
4. Diodes for EDS protection
5. Low pass filter for noise reduction
BU21025
GND
2
SDA
2.2kΩ
2.2kΩ
Master
( 2-wire serial
interface )
SDA
SCL SCL
INT GPIO
AD1
AD0
GND
○Product structure：Silicon monolithic integrated circuit
.www.rohm.com
© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・14・001
○This product is not designed protection against radioactive rays
1/15
TSZ02201-0Y2Y0F300050-1-2
7.AUG.2012 Rev.002
1 page  
BU21025GUL
Datasheet
Command Byte
BU21025GUL has a command byte after the address byte. Upper 4 bits of the command byte select an operation code. And
lower 4 bits of the command byte select an operand. Effects of the operands are changed by the operation code.
BIT
NAME
Table 2. Command Byte
MSB
LSB
76543210
C3 C2 C1 C0 O3 O2 O1 O0
BIT 7-4 : C3-0
Operation code:
BIT 3-0 : O3-0
Operand:
C3 C2 C1 C0
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
It is select an operation of the command. Detail is shown in Table 3.
It has 3 types. The operand type is selected by the operation code. When the operation
code is not “0101” or “1011”, the option type is 0. When it is “1011”, the option type is 1.
When it is “0101” option type is 2. Detail is shown in Table 3 and 4.
Table 3. Operation Code Function
FUNCTION
AD-INPUT X-DRIVER
Set Power
Reserved
Measure AUX
Reserved
Set Power
Software Reset
Reserved
Reserved
Drive X
Drive Y
Drive Z
Setup
Measure X
Measure Y
Measure Z1
Measure Z2
OFF
-
AUX
-
OFF
OFF
-
-
OFF
OFF
OFF
Keep
YP
XP
YN
XP
OFF
-
OFF
-
OFF
OFF
-
-
ON
OFF
XN-ON
Keep
ON
OFF
XN-ON
XN-ON
Y-DRIVER
OFF
-
OFF
-
OFF
OFF
-
-
OFF
ON
YP-ON
Keep
OFF
ON
YP-ON
YP-ON
INT
POLARITY
H
-
H
-
H
H
-
-
L
L
L
Keep
L
L
L
L
OPERAND
TYPE
0
-
0
-
0
2
-
-
0
0
0
1
0
0
0
0
Set Power (0000, 0100)
This code is used for returning to a state for touch detection without A/D conversion after sending screen drive command.
After this command, A/D converted data is set to 0.
Software Reset (0101)
BU21025GUL resets an A/D converted data, setup settings, and state of analog blocks to the initial state. If BU21025GUL
receives this code during an A/D conversion, the A/D conversion is stopped.
Drive X (1000), Drive Y (1001), Drive Z (1010)
BU21025GUL starts driving screen voltage by each code. PD is not effective. So, Driving is continuous until reserving
another command that changes state of driving screen voltage.
Measure AUX (0010), Measure X (1100), Measure Y (1101), Measure Z1 (1110), Measure Z2 (1111)
BU21025GUL starts driving screen voltage and A/D conversion. A PD of operand set,state of BU21025GUL after A/D
conversion is finished.
Setup (1011)
The setup command has a special operand (type is 1). The operand has MAF and pull-up resistor settings. Detail is
shown in Table 4.
www.rohm.com
© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
5/15
TSZ02201-0Y2Y0F300050-1-2
7.AUG.2012 Rev.002
5 Page 
BU21025GUL
Datasheet
●Operation
Position Detection of Touch Screen
The 4-wire resistive touch screen is mainly constituted in two resistive plates, X and Y. If screen is pressed, these 2 plates
are connected.
A position of touch screen is detected by applying voltage to one plate and measuring voltage of another plate. This
measurement voltage is divided by touch position. In X-position detection, X-plate is applied voltage. And Voltage of Y-plate
is measured. In Y-position detection, Y-plate is applied voltage. And Voltage of Y-plate is measured. The master needs to
detection 2 times for detecting X and Y position
When screen is not touched, a measuring plate is high impedance from another plate. So, it can’t get voltage. And a value
of the A/D conversion became unknown. If unknown values are used for calculating the coordinates, the coordinates will not
show touch points. So it is require to filter unknown values when the calculate coordinates.
VDD VDD
ON
XP
YP
ON
XP
YP
VREFP
VREFP
AIN AIN
VREFN
VREFN
XN
YN
ON
XN
YN
ON
GND
Figure 5. X-Position Detection Mode
GND
Figure 6. Y-Position Detection Mode
Touch Resistance Measurement
These are two methods for measuring touch resistance. The first method requires that a resistance of X-plate (RX-plate) is
known. In this method, the calculation of touch resistance (RTOUCH) needs X position and 2 additional measurement data (Z1
and Z2) that shown in Figure 7 and 8. The equation is as follows,
R TOUCH
= R X-plate
⋅
Xpostion
4096
⎜⎜⎝⎛
Z2
Z1
−1⎟⎟⎠⎞
The second method requires that both resistance of X-plate and resistance of Y-plate (RY-plate) are known. In this method,
the calculation of RTOUCH needs X and Y position and Z1. The equation is as follows,
R TOUCH
=
R
X-plate - Xposition
4096
⋅
⎜⎜⎝⎛
4096
Z1
−1⎟⎟⎠⎞ - R Y-plate
⋅ ⎜⎜⎝⎛1-
Yposition
4096
⎟⎟⎠⎞
VDD VDD
ON
XP
YP
ON
XP
YP
VREFP
AIN
VREFN
XN
YN
ON
GND
Figure 7. Z1-Position Detection Mode
www.rohm.com
© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
11/15
VREFP
AIN
VREFN
XN
YN
ON
GND
Figure 8. Z2-Position Detection Mode
TSZ02201-0Y2Y0F300050-1-2
7.AUG.2012 Rev.002
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet BU21025GUL.PDF ] | |
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